title: Identification of an iron acquisition machinery in Flavobacterium columnare.
abstract: Flavobacterium columnare, a fastidious Gram-negative pathogen and the causative agent of columnaris disease, is one of the most harmful pathogens in the freshwater fish-farming industry. Nevertheless the virulence mechanisms of F. columnare are not well understood. Bacterial iron uptake from the host during infection is an important mechanism of virulence. Here we identified and analyzed part of the iron uptake machinery of F. columnare. Under iron-limited conditions during in vitro growth, synthesis of an outer membrane protein of ~86 kDa was upregulated. This protein was identified as a TonB-dependent ferrichrome-iron receptor precursor (FhuA). Synthesis of siderophores in F. columnare was corroborated by chrome azurol S assays. A putative ferric uptake regulator (Fur) protein was also identified in the F. columnare genome. Structural analysis of the F. columnare Fur protein revealed that it was similar to Fur proteins involved in iron uptake regulation of other bacteria. Furthermore, Salmonella enterica serovar Typhimurium (S. Typhimurium) Δfur mutants were partially complemented by the F. columnare fur gene. We conclude that a siderophore-mediated iron uptake system exists in F. columnare, and fur from F. columnare could partially complement S. Typhimurium Δfur mutant.
authors.affiliation: The Biodesign Institute, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: Lingyu
authors.initials: L
authors.lastname: Guan
authors.forename: Javier
authors.initials: J
authors.lastname: Santander
authors.forename: Melha
authors.initials: M
authors.lastname: Mellata
authors.forename: Yuangxing
authors.initials: Y
authors.lastname: Zhang
authors.forename: Roy
authors.initials: R
authors.lastname: Curtiss
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001692:Biological Transport / Q000502:physiology; D005417:Flavobacterium / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D007501:Iron / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017262:Siderophores
chemical_list: D001426:Bacterial Proteins; D017262:Siderophores; D007501:Iron